To be quite honest with you, to borrow a line from a song, "It's all the same, only the names change."
A ship that is "good" today can suck in 6 months with a new CO, XO, RO, DMC, you name it. They all ride cycles; one ship might be operating well now and in a year might have MTT or NR living onboard. Chances are that whatever ship you get, you will have a cycle of each.
I would first think about where you would like to live. You should get a little time in port, so what part of the country is best for the things you like to do? The choices are very different from each other, and I have been in all 4 carrier ports. Is it important for you to be close to family? You have to take that into account as well if that is important to you.
Where do you want to visit? If Hong Kong, Singapore, and other Pacific ports sound interesting, then you want a west coast ship. Europe or the Caribbean? East coast ships go there.
You will find someone on each ship that will tell you that it sucks. Having been on several carriers, I will tell you that, ship to ship, there aren't that many differences.